<template>
  <div class="pagination">
    <!-- 上 -->

    <button :disabled="pageNo == 1" @click="$emit('getPageNo', pageNo - 1)">
      上一页
    </button>

    <button
      v-if="startNumAndEndNum.start > 1"
      @click="$emit('getPageNo', 1)"
      :class="{active: pageNo == 1}"
    >
      1
    </button>

    <button v-if="startNumAndEndNum.start > 2">
      ...
    </button>

    <!-- 中 -->
    <button
      v-for="(page, index) in startNumAndEndNum.end"
      :key="index"
      :class="{active:pageNo == page}"
      v-show="page >= startNumAndEndNum.start"
      @click="$emit('getPageNo',page)"
    >
      {{ page }}
    </button>

    <!-- 下 -->
    <button v-if="startNumAndEndNum.end < totalPage - 1">...</button>
    <button 
    v-if="startNumAndEndNum.end < totalPage"
    @click="$emit('getPageNo',totalPage)"
    :class="{active:pageNo == totalPage}"
    >
      {{ totalPage }}
    </button>
    <button
    :disabled="pageNo == totalPage"
    @click="$emit('getPageNo',pageNo + 1)"
    >下一页
    </button>
    <button style="margin-left: 30px">共{{ total }}条</button>
  </div>
</template>

<script>
export default {
  name: "Pagination",
  data() {
    return {
      property: "value",
    };
  },
  props: ["pageNo", "pageSize", "total", "continues"],
  methods: {},
  //计算属性
  computed: {
    //总共页数
    totalPage() {
      // ceil向上取整
      return Math.ceil(this.total / this.pageSize);
    },
    //计算页码的起始数字
    startNumAndEndNum() {
      //结构
      let { pageNo, totalPage, continues } = this;
      //先定义两个变量,存储起始数值
      let start = 0,
        end = 0;
      //连续的页码数<5,就是不正常页面,就需要判断
      if (continues > totalPage) {
        (start = 1), (end = totalPage);
      } else {
        // 大于5为正常现象
        // 开始数据
        start = pageNo - parseInt(continues / 2);
        // 结尾数据
        end = pageNo + parseInt(continues / 2);
        //纠正start为-1
        if (start < 1) {
          (start = 1), (end = continues);
        }
        //end数值>总页码
        if (end > totalPage) {
          end = totalPage;
          start = totalPage - continues + 1;
        }
      }
      return { start, end };
    },
  },
};
</script>

<style lang="less" scoped>
.pagination {
  text-align: center;
  button {
    margin: 0 5px;
    background-color: #f4f4f5;
    color: #606266;
    outline: none;
    border-radius: 2px;
    padding: 0 4px;
    vertical-align: top;
    display: inline-block;
    font-size: 13px;
    min-width: 35.5px;
    height: 28px;
    line-height: 28px;
    cursor: pointer;
    box-sizing: border-box;
    text-align: center;
    border: 0;

    &[disabled] {
      color: #c0c4cc;
      cursor: not-allowed;
    }

    &.active {
      cursor: not-allowed;
      background-color: #409eff;
      color: #fff;
    }
  }
}
.active{
  background-color: #409eff;
}
</style>
